Gunsight having lead computing device



p 9, 1952 c. s. DRAPER ET AL GUNSIGHT HAVING LEAD COMPUTING DEVICE 2 SHEETS-SHEET 1 Filed April 27, 1942 INVENTORS, C. S. DRAPER,&E.P. BENTLEY SP0 7 77/V6 COR/H 6 7/0/76 CORREC 770 H ATTOR EY.

C. S. DRAPER ET AL SIGHT HAVING LEAD COMPUTING DEVICE Sept. 9, 1952 GUN Filed April 27, 1942 2 SHEETS-SHEET 2 INVENTORS, C.S. DRAPER& E. F! BENTLEY,

Patented Sept. 9, 1952 oousronr HAVING LEAD COMPUTING DEVICE Charles S. Draper, Newton, and Edward P. Bentley, 'Wollaston, Mass, assignors, by mesne assignments, to Resea ration of New York rch Corporation, a corpo- Application April 27, 1942, Serial No. 440,660

42 Claims. (01. cans) This invention relates to lead computing or rate measuring devices, particularly, though not exclusively, useful in fire controlapparatus for the aiming of guns such as antiaircraft guns,

Where the speed of the target is relatively great.

This application is a continuation in part of our co pending application Serial No. 385,916, filed March 29, 1941.

In apparatus to control fire at a moving target,

it is necessary'to advance the line of fire with respect to theline of sight by an angle depending on the speed of the target and on the time of flight of the shell. Many forms of rate devices have been suggested for this purpose. One form, which may be termed the director type, utilizes a manually driven sighting device which controls the motion of the gun mount through some a kind of servo-mechanism. This has the disadvantage :of controlling the power for operating a massiveelement from the operation of relatively light parts, with the result that the equipment involves excessive complication.

Inanother suggested form, which may be called the disturbed sight type, the primary source of power is applied to the gun element, the motion of which .is applied to the sighting element through .a rate device, for introduction of the lead angle. In theory, this avoids some of the difibculty of the director system, but so far as we are aware, apparatus of this kind has not proved successful. The force or torque applied to the V sightingelement is determined by the motion of the gun, but the operation of the system is controlled by the gunner in accordance with the motion of the line of sight. Whenever the line of sight does not move at a constant angular ve-' locity, a false prediction isgiven by reason of the difference between the angular velocity of the line .of fire and that of the line of sight; furthermore, the system may be unstable in that transients, when once introduced, will not decay pose to control the line of sight in accordance with the ,ratefloi movement of the gun (which may be're'al or dummy) by means of a springcentralized gyro element "constructed in accordance with a correct relation between the several physical quantities, as will be hereinafter de-" scribed in detail. It may here he briefly mentioned that the quantities affecting the precessional displacementof the gyro are the moment of inertia about the precession axis, the coefficient of damping for angular displacement about said axis, and the elastic coeflicient of-the springs opposing said angular displacement;

One of the requirements is that the moment-of inertia shall be small and that. the damping coefiicient and the elastic constant shall be relatively large. Likewise important is-a relation between the damping and elastic coefiicients whereby the prediction error caused by angular acceleration is neutralized, and stabilityis'maintained. It is also an essential feature of; our invention that, when. stable conditions have been once established, they are maintained under all possible circumstances of operation. We also employ a new and improved type of rate gyroscope, sincethe conventional type does not give a sufficiently accurate. indication; forthe purposes of this invention, The indications given by conventional gyroscope indicatorswhichluse ball bearings for suspendingthe gimbal'frame are particularly subject to. errors for small angles of precession. The type of gyroscope'w'e, prefer to employ is an improvement in the typeshownin the co-pending application of C. S. Draper, now reissue patent 22,330,.dated June 8, 1943, in which no bearings in the ordinary sense are employed for supporting the gimbal frame.

, Another feature of .our invention is the use of means for applying what may be termed a bias torque to thegyro to compensate or correctffor the effects of gravity, wind, etc. acting on the shell. This means may be embodied in. several forms, one of which .is particularly useful in automatically applyinga proper superelevation for correction of gravity in any position offthe gun. 1

Referring to the drawings illustratingthe preferred form of our invention, Fig. 1 is a diagramthrough the forward spring suspensiongofgthe gyroscope; Fig. 5is a section through one off'the oil-dampers employed on the optical mirrors; Fig. 6 is a perspective View showing the 'compl'ete sight as mounted on the gun; Fig. 7 is adetail, in perspective, showing a modified method oil ntroducing acceleration corrections, such as those due to winder gravity; Fig. B'sho'wsastill"further which remains parallel to the gun bore.

modification in such corrections; and Fig. 9 is a perspective view of a modified form of rate gyro.

As shown in Fig. 6, the entire sight and computing unit may be housed in a box I which may be directly mounted on the gun 2 or a dummy gun, i.'fe., an object mounted for orientation in azimuth and tilting in elevation about a normally horizontal trunnion axis.

and for similar adjustment in elevation about normally horizontal trunnions 5, 5. For the-sake of simplicity, such details as the shock mounting axis 5--5. The gunner, with his eye at 8, looks through this mirror directly at the target, and

" also sees an image 9 of the reticle 9 reflected onto the surface of the mirror 8 from a second mirror III, as illustrated by the dash-and-dot line. The mirror is also normally positioned at an angle of 45about the trunnion axis 12, The reticle'fis shown as in the form of crossed narrow slots l3 inan opaque disc 14 placed in the path of the beam from a lamp I and a collimating lens 16 which directs the image 9' of the reticle on mirror l0. Each mirror is preferably heavily damped about its axis ,of rotation, as by means of fixed oil containing housings H, H and slotted discs I8 within each (see Fig. 5), which are partially immersed in the oil I9 within the containers.

The optical system, being mounted on the gun, partakes-of allmovements thereof, but the. line of sight .is displaced with respect to the gun by the computing mechanism described below. In,

such mechanisms, the ultimate effect is always to advancethe axis of the gun ahead of the line of sight through the predicted angle i (Fig. 6), which may be resolved into prediction angles in train andin elevation. This advance in angle may be secured by displacingthe line of sight through an angle (X') with respect to the gun, as is done in the presentapplication, since the gunner, by always keeping the line of sight on the target, will thereby advance the gun through the angle A.

Two gyroscopes 20 and 2|, of the angular rate or two degree of freedom type, are shown, one of which is responsiveto tilt of the gun in elevation and the other to turning of the gun about an axis perpendicular to the gun barrel and to axis 5-5. In Fig. 1, the showing of the gyro- V scopes is simplified, reference being had to Fig. 2 forspecific constructional details, especially of the mounting, spring centralizing, damping and temperature maintaining devices for the gyroscopes. As shown in Fig; 1, the gyroscope 20 is mounted with its two degrees of freedom at right angles tothe gun trunnions 5, 5, i. e., it is barrel, with the spin axis 26 of the rotor 21 parallel to the trunnion axis 5, 5 of the gun, so that it is responsive to turning of the gun in traverse The gun is shown as mounted in the usual manner on a base 3 for rotation in azimuth about .a normally vertical axis 4 by any suitable mechanism (not shown) or, more precisely, in the slant plane containing the axis 5-5 and the axis of the barrel 2, Therefore, angular movements of the gun in elevation will cause precession of the gyro 20 in one direction or the other, through an angle proportional to" said rateof 'movementagainst resilient centralizing means, hereinafter described, which rocks the arm 28 connected to trunnion 22, to

. thereby rock bell-crank lever 29 and thus rock 6, to give the same a displacement proportional the arm30 on the trunnion-shaft I of the mirror to the rate of turn of the gun in elevation, which is modifiedby the time of flight of the shell, as hereinafter described.

" Similarly, turning of the gun in azimuth (us ing-this term broadly) will cause movement of the arm 28' connected to the trunnion to rock the arm 3| connected to the trunnion l2 of the mirror [0, which has the effect of displacing'the line of sight in this plane due to the 45 mounting of the two mirrors 6 and [0. As shown in the drawings, the linkage 28, 29, 30'and 28', 3| connecting the two axes of th prediction gyroscopes with'the optics together with the doubling effect of the reflectors markedly multiplies the very small angular movements of the gyroscopes so that a minute precession of 'eachgyroscope results in a much larger angular movement of the optics. The importance of this multiplication, as

pointed out in the aforesaid prior application isthat we limit the maximum precession of the gyroscopes in each direction to a very small angle as compared to the practice in -the prior art so as to reduce the errors introduced by the large angles of precession of the gyroscopes away from their central position that would otherwise occur in i order to obtain the correct prediction angle for We therefore employ th aforesaid the Optics. 7 multiplying linkages in addition to the optical multiplication and are thus able to confine the precession of the gyroscopes to an angle on the order of less than two degrees.

Preferably, bothgyroscopes are" spring centralized and pivotallysupported by novel spring suspension means similar to that described in the prior application of Draper and Bentley hereinbefore referred to, and first described in the aforesaid patent of C. S. Draper, the, present mounting being an improvement over the mountings of the said prior applications. According to the present invention, one trunnion, shown as the rear trunnion 22' or 25', of each, gyroscope is spring supported and centralized by means of a plurality of tangentially directed leaf springs 32, 32', 33, 33, symmetrically arranged around each trunnion and connected thereto by radially extending connecting members 34 and 35 which are shown as in the form of wires passing through a clamp or block 36 secured to the trunnion. At the two outer ends, each wire is clamped in other blocks 31,31, 38, 38', which are also clamped adjacent the free end of respective leaf springs 32, 32', 33, 33'. In Fig. 3, the bending or leaf springs 32, 33 are shown as, anchored to the casing by being clamped in ears 42 extending from the rear end of the casing. It will readily be seen that upon precession of the gyroscope, each trunnion will be turned, thus twisting the wires 34, 35 and pulling their Outer ends inwardly against the spring force. of the relatively stiff leaf springs.

' While this resistance to precession is mainly exforce exerted due to the'jbending of-the wires themselves.

precessional'movements- It isiinpontant that the damping coefiicient ilhexopposite tr/minions 40f rthetgyroseopaehowever, .areipreferablyjsupported and spring centrall'zed tby adiiferent type or tension-wirewhich "also iactsito eprevent axial displacement of *the trunnions. In other wordstthis wir'e-alsoaacts to pass around the inner U-arm 45'. Said frame 16 at its outer end-is shownas clamped to the middle of the wire 44 by clamp screw 41. This 'wire'tlierefore erases a pivst upport forthe rotor bearing "frame- 40 at its for-ward end: Also,

by. its resistance to. twisting, it acts-as aresilient;

centralizer for the frame to oppose precession,

and in the -th-ir-l:l plaee, it prevent axial shift of the rotor bearing frame "'in either direction, thus supplementing the action of the new spring and wire members at the other end, which have little axial resistance. As explained above; the total centralizing force, exertedbythe springsis quite largey being much- "greater than that normally employed in rate of turngyroscopes, in order to limit the angle precession of the gyroscopes to smallangles.

It is 1 snoimportant "that the -precess-i'onal movementsbe heavily *damped. Preferably the damper is of such a form that it also suppresses any bouncing or oscillation of the gyroscope in its spring supports. Such damping means is shown: as in the -form of circular -oil cont'ainers 4B placed at each=end"of the 'gyro casinget-and In order to introduce the=time of-iiight factdr,

We vary the sensitivity of the gyroscope, preferably by varying the spring force which opposes precession of the gyroscope. While this may be done by varyihgthetension'of the-leaf 'springs of Fig. 3, we prefer to utilize a separate spring system for this purpose. As shown, there is fixed to each trunnion 22', 25' an arm 53 carrying spaced knife edges "5'4 and Zia-each normally held between a pairot leaf springs '56; "56' and 51, *51" sothatthe bending force of the spring system opposes-crewhich are partially filled with heavy oil o --gum.

A disc-like member 'as' secured tothe trunnion or rotor frame is placed within each container. Preferably, th members 49 have axially extending or rim portions '50 at their periphery, the housing 48 closelyrsurrounding but not :touching the same. damping, resistance to "translatoryoscillations of the gyroframe in any plane,.-as i-wella's to rotary movements-due to precession. The rims also materially aid in the effective damping-cf the remain.substantially constant in order that the proper characteristic time of the-gyroscope may b preserved. To this-end, we prefer to incorporate inthe gyroehou-sing a means formaintaining the temperature of athe dampin fluid constant; which may -be achieved by utilizing electrical heating-coils 51, 7-52 rplaced next to "the oontainersa 48, controlled by a thermostaticmeans H39 adjusted to maintain a the; temperaturevat a fixed point higherthan would be -met-at any time from natural causes. A temperature wel above 100 is suggested for the purpcse- The term characteristic time referred to in the preceding paragraph may be: defined as the time the gyro would require toreach its position of :equilibrium or" rest when subjected to a -sudden change in angular "velocity; if it were to maintain its initial. rate oiqprecession until it reached "such .positi'on'. 'We 'haveifound that for l proper performance, the characteristic time of the gyroscope should be'ar' a definiteeirelatiom' ship to the time :of iiiigh't of the 'shellgi. c, it should never: be "less-than but at least equal 'to the time of flight as otherwise the gyro will'not These discs thereiore interpose a.

cession of the gyro in each direction. rt vary this bending force withthe time of flight or range, we have shown each pair of springs as mounted on an adjustable bracket 58, 58", and the two brackets are movableeq'ually andoppo'sitely, as "by being providedwith op'positely'facing rack'bars -'59,-59" 'meshingwitha com-men pinion Ell o'n the shaft o fagearfil.

ilt vim r readily e apparent thattyf rctat ng said} gear, the stiffness fo'f the springs may :be readily varied. For this purposa thereis shown a'time-df-flight or range dial G2 whichis shown 'as turn'ing the gear Bl through'a "suitable gear connection 63. Preferably, a single'r'angesettiiig shouldbe used to shift the spring system equally bn'bctng rqscopes. For t iS IpuiposeQthe gear systems: is shownfas also meshing with a similar gear 6| on the "shaft of a similar pinion 'fifl' meshing with the rack bars on the spring system on the other gyroscope.

For satisfactory operation of the apparatus described above,certainrelationships (within tolerable limits) between the physical constants must be maintained. These relationships are neces sary to prevent instability,- and also, to minimize the dynamic error under conditions of changing lead angle. These conditions will be best understood from the following mathematical discussion. This analysis may be carried out for one gyro only,'sinc e any motion may be resolved into components affecting the two gyros independentl'y. 7

Let: U I: the moment of inertia of the-rotor bearing frame and its rotor about the precession axis '22, 22', or 25, 25'. c=the coefficient of damping for angular displa'cementabollt Said a'XiS, or.

damping torque angular velocity of precession k=the elastic constant of the springs opposing angular displacement about said axis, or

= elastic torque (of spring) M deflection angle (angle of precession) #:the deflection (precession) angle or the gyro support about the precession axis from its nor mally central position; due t'o'a precession causing torque H=the angular momentum of the gyro rotor about itsspin axis (moment of inertia of-rotor angular yer-spin) wG=the angular velocity of w=the angular velocityof the line of sight ii zeoaeoc :Owing'toi'the ia'ctthat the gyro is mounted on "the gun, the precessional torque is proportionalto the angular velocity of the gun. Expressed symbolically, thisitorque'is HwG. But'the gunner operates the gunfrom'the line ofsight, and it isthe line of'sightwhich determines thelead prediction. "The angular'velocity of the gun is equal to the angular. velocity of the line of sight plus the rate of changeof the lead angle; that is,

. 1x G s I'he-precessional torque is,therefore,

Hw+H 2 The lead should be determined from the motion of the target which appears in the equation as the angular velocity of the line of sight. -,The quan- 1! maytherefore be considered as a false-prediction torque. .It has a definite value except when the angular velocities of the gun u 2 (A) the inertial torque I M di v I e the damping torque and I I V the elastic torquekd I Th A f a Y Y rgwj-iwaflrw d) I a =H( 4 This equation may be expressed throughout in terms of the lead angle x.

.-Let. S=thesensitivity:

indicated angle of lead I i I angular velocity of gun wq tog It i the last transformation being obtained from (3) by considering the condition of constant deflection angle.

1 Then and (4) becomes:

HI a CH (A H dk mat mn s* ?a (5) The false-prediction torque H can be entirely removed by making the dissipative or damping torque I i V 'dr I exactly equal" thereto. lActually; for reasons of stability. as will be presentlyexplained,'it'is desir able to introduce slightly more damping than is necessary to-wipe out the false-prediction torque.

For convenience, let,

It is important tonote: that-the damping-coeflicient'c is maintained constant, and that the sensitivity S is always inversely proportional'to: the elastic constant k, wherefore a-;is ,'a design constant of the equipment.

' Then (5) reduces to thesecond order equation:

.For constant angular velocity (and therefore 1 constant lead angle) the solution is simply 32s and since should'also be equal to Twi this means that S is made, by-calibration, equal to the time of flight (T) and the shell will meet the target atthe pointpredicted by the instrument. p I

, In general; however, the angular velocity is not constant. A'more complete solution can *be obtained :by standard methods if t is known as 1 a functionof time, and if his assumed constant,

asithwill be for any time-of-flight setting. For purposes of explanation, it will be suflicient to assume that the inertial torque is negligible, so

that (6) reduces to a first order linear equation:

I Without'going through the steps of integration, it may be shown that the solution of ('7) involves 1 (a) a transient term of the form L as where the constant C is determined from the initial conditions, and a (b) an error term, which may be called the forced dynamic error, due to acceleration effects, that is to say, departure of {w from a constant value. 1

Both the transient and forced dynamic error are zero if--a'=0. It should be noted, however, that 0' is even slightly negative, the transient will be one which grows indefinitely withincreasing time; in other words, the system is unstable and satisfactory operation would be impossible. The condition of negatives means that the false-prediction torque has not been completely wiped out by the dissipative torque.

Complete neutralization a=0) would leave the instrument 'on'the verge of'instability, with the possibility of unstable operation in the event of a slight change in any of the physical constants. Accordingly we make 6' slightly greater than'zero, that is, we not only neutralize the false-prediction torque but apply enough excess damping to insure stability under all conditions. 'When the a constant a has been once adjusted, it isconstant for all time-of-flight settings; -a change insensitivity S do'es not affect stability.

The forced dynamic erroris proportional to a S.

. :The constant if should therefore be made small. It has bee'nfound that the preferred value is in the neighborhood of 0.2, but values in the range v 'from 0.05to'0.50 have been found satisfactbryin practicew *r gyro Z I, regardless of thei'elevation of. the gun itthe arm 64., which will therefore, exerta torque endtnagym proportional to the sine ofthe inf clin-ation'of the trunnions 5, 5.. In this case too, the'Itorque varies in accordance with the cosine of' ithe elevation angle of the gun above the horizontal to provide the proper measure of super- I elvatloniTherefore these two components, en-

-teri'n together into the optical system, will give th'ejproper.superelevation angle.

'A' method of taking care of the effect of crosswind isto employ variable tension springs to exer. ato'rqueonifthe gyroscope, adjustable with cro wind" velocity, as illustrated in Fig. '7. In this ffigurathe U-shaped bracket 43 between the arms "of 'which the' centralizing wire 44' is stretched, is shown as adjustable about the wire as a center. For this" purpose, the arm is shown asprovided with segmental wormteeth 80 with which a worm 8| on shaft-82 meshes. By turning the knob 83' on said shaft to position a pointer 84 with respect to arbitrary wind velocity markings 8'5, a wind correction may be introduced.

Another method of introducing such correction is represented diagrammatically in FigsB.

Inthis'figurathe trunnion 25" of the gyroscope is provided with radial arms 86 carrying arc-shaped cores 8'! adapted-to enter solenoids 88. By variably exciting the solenoids, as by means of a rhcostat 89 having suitable graduations 90, the proper torque may be applied for wind or other corrections. I

While the corrective torque described in connection with either Fig. 7 or 8 may also :be applied to the elevation gyroscope 20, being made proportional to the head wind, i. e., the wind velocity along the line of fire (which has the effect of retarding or lessening the retardation of the shell), We prefer to introduce the correctionfor-head wind by introducing a correction for the same into the time of flight setting through knob 62."

= Spotting corrections are preferably introduced by-adjustment of the reticle with respect to the optical system with the gyroscopes in their centralized position, as shown in Fig. 1. The reticle isadju'sted in elevation by a setscrew 66 and in azimuth by aset screw 61, by which corrections for wind or spotting corrections may be easily introduced by adjusting graduated'knobs 66 and 61-; respectively.

The bias torques introduced as above described donot alter the dynamic characteristics of the system. This can be seen from Equation 4. If a constant torque is added to the precession torque' onthe right-hand side of the equation; the

criteria of stability are in no way affected.

The gyros are shown as air spun by means'of air nozzles 68and 69, and the speed of each'may" be carefully adjusted by the valves 10. Preferably, also, we place a thermostatically controlled air heater H in the air supply so that great fluctuations 'willnot occur in the temperature of the air supplied within the casing. A common pressure regulating valve is shown at 9|.

As many changes could be made in the above construction and many apparently widely different. embodiments of this invention could be made without departing from the scope thereof, it is .intended that all matter contained in the above description or shown in the accompany-- mg drawings shall. be interpreted as illustrative and'not me; limiting fsense. V "An example of one'fsuch modification' si trated in Fig; 9,; showing an "alternative" fornif be used ateach trunnion of the gyroscopafas shown at '44 and 92, and the radially extending wires 34, 35- omitted. Thus tension wire 92 is con-1'6 nected' at its middle to a cross bar 53? connect through the knife edge pins j54,*55' to the"'arm 53 connected to the forward trunnion, the wire 92- being, as beforejtightly held between supportsjf 95 and-96. Leaf springs ifi a nd' ilareflomitted" in Fig. 9 for the sake of clearnessf. therear, the wires may be supported in 'braclgetsfi, as. in Fig. 1,,the trunnion being securedto the mid dle portion of the wire through the open; frame 46'. .It will, of course, be understood that the damping discs'a'nd housings 48 are retained in all forms so as to damp the precession'of the gyroj'j scopev and suppress vibration and oscillation;- The feature of-applying a bias torque forpur" poses of correction is notlimited to the apparatus; in which the gyro is mounted on the gun but may be applied'to' any'type of lead computing or rate measuring gyroscope. The same is true of many i of the other improved features of ourdevicefsuch as the elevation and trunniontilt correcting masses 65 and 65, etc., as it isobvious that such inventions applyequally well to a lead-computing device whichmay bemounted on the sight itself or other target following device, instead of on the 1 gun.

Although the invention has been specifically described as-embodi-ed in a sighting devicefor guns, it will be understood that the invention is on the gun, it may of course be mounted on a dummy, ashereinbefore indicated, and the angles of elevation and train of the dummy may be transmitted to the real gun. In order to avoid repetition, it should be understood that we have used the word gun in the following claims as covering either an actual gun or a dummy gun or mount, as the two are equivalent so far as the construction and operation of our invention are concerned. Also, it should be understood that the terms spring, spring-like and resilient as used in the appended claims with reference to the resilient or yielding centralizing means acting about the precession axis of the gyroscope, are used in the broad sense of any meanshavingfthecentralizing properties of a spring, that is, which. exerts a torque on the gyroscope opposing precesli ,sion in either direction. from norm by a torque 1 proportional to the amount 'or ,angle' of precession'.

I Having thus described the-invention, we claim: 4 i

1. In a predicting deviceii'or fire control, the combination of a gun element and the sighting element therefor, a rate gyroscope mounted on the gun element for precession through an angle proportional to the rate of turn thereof, resilient means having an elastic constant (is) acting about the precession axis of said gyroscope for centralizing said'gyroscope, dampingfmea'ns also acting about the precession axis having a damp-, ing constant (c) opposing motion about the axis of precession substantially in proportion to the.

, 1 3:: velocity of the motion, said elastic-and damping constants having values such that I a where s is the sensitivity of the device, a d

means actuated by the precessicnalmovemehts of the gyro for introducingapredictionor lead angle between the gun and sighting elements proportional to said angle'of precession. I

2. In a predicting device for fire control; th combination of a gun element and the sighting element therefor, a rate gyroscope mounted on the gun element for precession through an angle proportional to the rate of turn thereof, resilient means having an elastic constant (k) for cen-' tralizing said gyroscope, damping means having a damping constant (c) opposingfmotion about the axis of precession substantiallyin proportion to the velocity of the motion, said elastic and damping constants having values such that sighting elements proportional to said angle of precession, resilient means having an elastic constant (k) for centralizing said gyroscope, and damping means having a damping constant (c) opposing motion about the axis of precession substantially in proportion to the velocity of the motion, said elastic and damping constants having values such that V I i i c pkS is between 105 and 1:50;- where S is the sensitivityof'thedevice, saidva'lue-of being maintainedsubstantially constant for all sensitivity settings by adjusting in inverse proportion to 10.

4. In a gyro sight, a target following device including gun and sight elements, a spring-centralized rate gyroscope adaptedto be mounted on said device mounted for turning in azimuth and for turning zip-elevation about a normally horizontal trunnion-axis, .said gyroscope being mounted for precession about an axis perpendicular :tosaid trunnion axis by reason of and upontangular S substantially movements of said device in elevation, means actuated from said gyroscope for introducing a predicted correction in elevation between the sight and; gun variable with angular velocity" of said, devicehandfla m ss c ntric-ally, securedto said sym con rwith r spect to sai precession, axisand fiiwAvgyro, sight, as 'claimed in-claim 4, having a second, gyroscope mounted .for: precession; about sp rallelatc:the precession axis or than sth said second gyroscope which exerts a torque thereon only when the trunnion axis of said device inclined to'the horizontal, a means'connectingboth gyroscopes to the sight element to give thesame a lead angle in both train and elevation.

6. In a prediction or lead computerof the an gular rate type for guns, a lead angle indicating device, a pair of gyroscopes adapted-to be mountedon the gun,one mounted forprecess-ion upon turning of the gun in elevationand the othermounted for precession upon turning of the gun in the slant plane determined by itstr-unnionand bore axes, means connecting both gyroscopes-tc+ the indicating device to cause movement thereof i proportional to the precessionalmovements of the-gyrescopes, a superelevation weight secured to the first named gyroscope and adapted 'to exert Y thereon a torque proportional to the cosine of the angle of elevation, anola superelevation weight: secured to the other gyroscope adapted to exert thereon a torque proportional to"thesine=of the inclination angle of said trunnion axis;

'7. In a prediction mechanism for guns, a'pair of gyroscopes'mounted on a target 'following de vice, said device including a lead angle indicating mechanism, onegyroscope being mountecltorpre} cession upon turning of the gun inelvation and-- the other mounted for precession upon turning of the gun in the slant plane determined by its trunnion and bore axes, means connecting the gyroscopes to the indicating mechanism to cause movementthereof proportional to the-precessional ,movements of the gyroscopes; and means for applying a biasing torque about the precession axis of the latter gyroscope proportional to the comfl ponent wind velocity acrossthe line of fire.

8. Prediction mechanism for gunsas claimed in claim 7 wherein said biasing torque-means in; cludes an electromagnetic torquer-and means for varying the energization thereof proportionally to the'cornponent of wind'velocity across the line of sight.

9. In a prediction or lead; computer of .the angular rate type for guns, a gyroscope adapted to be mounted on a target following device for precession about an axis'due to and upon movement of the device in elevation, a sight operated in ace cordance with the precession, resilient centraliz ing means for opposing precession in eitherdb rection, means for adjusting the preces-sional sen sitivity of the gyroscope for varying ranges, mfi lfi for altering the normal centralized position of the a gyroscope for applying wind corrections, and means for giving the sight a lead angle relative to the gun from theprecession' oi said gyroscope while said device is following a target.

means for opposing precession in either direction, and means for introducing a superelevation correction comprising a mass eccentrically secured to said gyroscope with respect to the, precession axis and adapted to exert a torque thereon vary,-

ing with a function of the angle of elevation of the device. ll. ina prediction or lead computer of the an-r A gular rate type for guns, a gyroscope adapted to be mounted on a target following devicefor prea. I

cession about an axis due to and upon'movement :Q th w dfivigfi ILthislant planmdeterminediby its:

barrel an trunnions, resilient centralizingmeans for opposing precession in either direction, means for adjusting the precessional sensitivity of the;

gyroscope for'varying ranges, and-an eccentric mass secured to said gyroscope above its precession axis and adapted toexert a tqrquethereon when said trunniqnaxis is inclined to the hori- Zontalproportional to;the sine of the angle of i cl ati r r 12.. In a; gyroscopic lead computer for gun sights, a spring-centralized gyro movable ,with

said sight andhavingan axis of rotation perpendicular to said axisof movement, an indicating,,device operated by ,precession of the gyro, a

spring centralizer for the gyro, torsion means for the spring centralizer to apply a bias torque to the gyro about the axis of precession thereof, and means for adjusting said means to correct for cross wind,

1 3. In a gyroscopic lead; computer for gun si h s, aspiring-centralized gyro movable with saidfsight andhaving an axis of rotation perpendicular to said, axis of movement, anindicating device operated by precession of the gyro, a spring centralizer for the gyro, and torsion meansfor the spring, centralizer to apply a bias torqueto the gyro about the axis of precession thereof, said torsion means -includinga solenoid and a core,

attracted t herew and connected with said centralizer 14 In aj 'gyroscopic lead computer for gun sights, an angular rate gyroscope includingarethe gyroscope and having thermostatically controlled means .for maintaining the temperature and thereby the viscosity thereof.

15.In a'pre'dicting device for fire control, a sight comprising adjustable means defining a line ofsight, a rotatable support, means for mounting said sight for displacement relative to the support, a rate gyroscope mounted on said support for precession in proportion to the rate of rotation of the support, a resilient restraint opposing precession of said gyroscope and having an elas-' tic'coefficient K, means damping precession of said gyroscope, and means for adjustingrsaid re sil ient restraint, to alter the amount of displacement of the line of sight relative to thesupport upon precession of said gyroscope, 'saidadjust menthaving a sensitivity constant S with respect to the rate of rotation of said support, said damping means having a damping constant c, and said constants having the relationship 16. A lead computing device to compute an an-' thereof and having a sensitivity S, connections foroperating the line of sight element in accordance with; the precessionrto introduce an angle A between the driven element an dpthe line .pfisight element, whereby the device is subject toan, m1,

stability-producing torque which is a function of resilient centralizing means "having an elastic cof eflicient K opposing the precessional *torque of the gyro, and means for applying about the axis of precession a dissipative torque of coefficient c proportional to I dx dt and to KS to neutralize the instability producing torque.

l7, Alead computing device to compute anangular lead betweenaprimary driven element and an indicating element comprising an angularrate gyro to be bodily turned with the driven element i and capable of precession through an anglesubstantially proportional to the rate of turn thereof, connections for operating the indicating element from and in accordance with the precession to introduce an angle A between the driven element 1 and the indicating element, whereby the device is subject to an instability-producing torque which is a function of a di resilient centralizing means having an elastic constant k to oppose the precessional torque, and means for applying about said axis a damping torque proportional to digs dt the damping means having a damping coefficient c, the relation of the constants being such that driven element and capableof precession through Y an angle substantially proportional to the rate of turn thereof, connections for operating the line of sight element in accordance with the.

precession to introduce an angle A between the driven element and the line of sight element, whereby the device is subject to an instabilityproducing torque which is a function of resilient centralizing means opposing the precessional torque of the gyro, means for applying about the axis of precession a dissipative torque proportional to to neutralize the instability producing torque,-

and means for adjusting the sensitivity S in inverse proportion to the elastic 'coeflicient k,

whereby stability is uniformly maintained without variation of the damping coefficient. i

19. A lead computing device to compute an angular lead between a primary driven element and an indicating element comprising an angular: 1 retegyroto be bodily turned with the drivenix 'elementand capable of precession through an "angle substantially proportional to the rate of turn thereon connections for operating the indicating element in accordancewith the preces sion tointroduce an angle x between the driven element and the indicating element, whereby the device is subject to an instability-producing torque which is a iunction of vresilient centralizing means having an elastic constant k to oppose the precessional torque, and

means for applying about said axis a damping torque proportional to theidamping means havinga damping coefficient c, the relation of the constants being such that isa constant between 1.05 and 1.50, where S is the sensitivity of the device.

20. A lead computing device to compute an angular lead between a primary driven element and a line of sight element comprising an angular rate gyro to be bodily turned with the driven element and capable of precession through an angle substantially proportional to the rate of turn thereof, connections for operating the line of sight element in accordance with the precession to introduce an langle Xbetween the driven element and the line of sight element, whereby the device is subject to an instability-producing J torque which is a function of i kS is a constant between 1.05 and 1.50, where S is the sensitivity of the device, and means for adjusting the sensitivity S in inverse proportion to the elastic coefiicient k, whereby'stability is uniformly maintained. Without variation of the damping coefficient.

21...A predicting devicefor laying a gun in elevation froina line of sight comprising a rate gyro mounted to be bodily turned in elevation with a gun and capable ofprecession through an angle substantially proportional to the rate of turn thereof, means for applying to the gyroscope about theaxis of precession a stiffness or centralizing torqueand adissipative torque, means for computing a lead angle in elevation therefrom including connections'for causing theline 10f sight to lag behind the turning of the gun from the gyro precession in accordance with the amount of precession, and means forapplying about the axis of precession of said gyro a superelevational biasing torque to the gyro proportional to gravitational force and to the cosine of the angle of elevation.

'22.A predicting device for fire control com I8 prising a rate gyro mounted to be bodily turned in elevation with a gun and capable of precession through an angle substantially.proportional to the rate of. turn thereof, means for applying about the axis of precession a stiffness torque and a. dissipative torque, lead angle indicating means, connections forpoperatingrthe indicating means from thegyro in accordance with the precession, and a mass mounted on said gyro eccentrically with respect to said axis to introduce a superelevational correction to the ro proportional to the cosine of the angle of elevation. V i

23. A predicting device for fire control, as claimed in claim 21, having a second gyro having its spin axis normal to the spin axis of the first gyro and adapted to be turnedin azimuth with the gun and capable of precession upon such turning movements, means for computing a lead train angle therefrom including connections for causing the line of slghtto lag behind. the turning of the gun in accordance with the precession of said second gyro, and means for applying about the precessionaxis of said second gyro a biasing torque due to gravity only when the spin axis of said second gyro is inclined from horizontaL.

24. A predicting device for fire control as claimed in claim 22, havinga second gyro having its spin axis normal to the spin axis of the first gyro and adapted .to be turned in azimuth with turning movements, connections for operating the indicating means from said second gyro-in ac- .cordance withtheprecession of saidsecond gyro, z and means for applying about the precession axis of said second gyro-a biasing torque due to gravity ;and proportional to the sine of the. angle of inclination of the spin axis of said second gyro from horizontal.

25. In a lead computer of the angular rate type, a rate of turn gyroscope, means for resiliently centralizing the same, lead indicating means actuated by precession of said gyroscope,

means for introducing across wind correction into said-computer, said means includingmeans for shifting the null positionajof the. centralizing, means for altering the normally centralized position of the gyroscope and a scale representing cross wind velocity by which the centralized sights, an angular rate gyroscope including a resilient restraint opposing precession thereof, said gyroscope being adapted to be mounted on a gun for precession against the opposition of said restraint. through an-angle proportional to the rate of turn of the gun, means operated from said gyroscope in accordance with such precession for imparting-aproportional negative lead angle to the sight, and damping means modifying the responseof the gyroscopic'precession to change of velocity of the gun so constructed and arranged with respect to the resilient restraint as to prevent saidlead angle from changing at a --rat-e greater than the angular velocity of the gun, said damping means including a viscous drag device acting about the precession axisof thereto .at Spaced points so as to pivotally support and yieldingly centralize said frame, and a two-part liquid damper for said gyroscope, one part of which is rotatable with said gyroscope and comprises a disc having an axially extending flange, the other part comprising a closely fitting housing for said disc and flange, whereby translatory vibration of the gyroscope in all directions is damped by said damper as well as the precession thereof.

28. In an angular rate gyroscope, a rotor, a bearing frame within which said rotor is mounted for spinning about an axis, an outer casing,

' means for pivotally mounting said frame in said casing for precession about a second axis without a bearing, comprising only spring means extending between said frame and said casing for both pivotally supporting and guiding the frame and yieldingly opposing the precession of the gyroscope in either direction from its normal position, a disc on said frame for turning therewith having an axially extending flange, and a closely fitting liquid container surrounding said disc and flange and secured to said 'casing, whereby transitory vibration of the gyroscope in all directions as well as gyro precession is damped through the action of said liquid filled container on said disc and flange.

29. An angular rate generating device for fire control, comprising a gyroscopic rotor and rotor bearing frame, means furnishing a trunnion axis therefor including a plurality of springs for .pivotally supporting and resiliently centralizing the same, damping means both for strongly damping precessional movements of said frame about said axis and for suppressing vibrating motion of said frame, and means for adjusting the bending tional straight leaf spring for additionally cen-' tralizing the gyroscope, and -means for varying the effective length of said straight spring for adjusting the bending stiffness thereof in accordance with the range.

31. In a predicting mechanism for a' disturbed sight, the combination with a sight adapted to be mounted on a gun, means for causing said sight to lag behind the gun at an angle equal to the predicted lead'angle, including a rate of turn gyroscope adapted to be mounted on the gun, resilient means for strongly centralizing the same about its precession axis, viscous means for heavily damping the same about said axis, the damping coefficient having a critical relationship'to the other constants of the gyroscope, and means for accurately adjusting the damping coefficient for establishing and maintaining such relationship,

resilient means with range, and means for introducing a superelevation correction, which is correctv without adjustment for all normal ranges, comprising a mass eccentrically secured to said gyroscope with respect'to the precession axis and adapted to exert a torque thereon varying; with a function of the angle of elevation of the device.

33. In a gyro sight, a target following device including gun and sight elements, a spring-centralized rate gyroscope adapted to be mounted on said device mounted for turning in azimuth and for turning in elevation about a normally horizontal trunnion axis, said gyroscopebeing,

mounted for precession about an axis perpendicular to said trunnion axis by reason of and upon angular movements of said device in elevation, resilient means for opposing such precession, means for varying the stiffness of said resilient means in accordance with range, means actuated from said gyroscope for introducing a predicted correction in elevation between the sight and gun variable with angular velocity of said device, and a mass eccentrically secured to said gyroscope with respect to said precession axis and adapted to exert a torque on thegyroscope about said axis proportional to the cosine of the angle of elevation of said device about its trunnion axis, whereby said mass exerts correct superelevation erection regardless of range.

34. In a prediction or lead computer of the angular rate type for guns, a gyroscope adapted to be mounted on a target following device for precession about an axis due to and upon movement of the device in elevation, resilient cen+ tralizing means for opposing precession in either direction, damping means for imposing a flxed drag upon such precession, means for introducing a superelevation correction comprising a mass eccentrically secured to said gyroscope with respect to the precession axis and adapted to exert a torque thereon varying with a function of the angle of elevation of the device, and means for varying the stiffness of said centralizing means with range, whereby the correction introduced by said mass remains correct for all ranges.

35. An angular rate generating device for fire about said axis, means for adjusting the stiffness of at least one of said leaf spring in accordance with range, and means for maintaining the strength of the damping 'means substantially constant.

37, An angu lar rate generating devicefor fire control, comprising a gyroscopic rotor and rotor 21 may be made substantially equal to the time of flight of the shell.

38. An. angular rate gyroscope comprising a gyroscope and rotor bearing frame, a pivotal support mounting said frame for precession including a trunnion, a plurality of springs at said trunnion and connected thereto so as to pivot-ally support and resiliently centralize said frame, and

means for adjusting the stiifness of at least one of said springs for changes in the time of flight of the shell, and a two part liquid damper for said gyroscope, one part of which is rotatable with said gyroscope and comprises a disc having an axially extending flange, the other part comprising a closely fitting housing for said disc and flange, whereby translatory vibration of the gyroscope in all directions is clamped by said damper as well as the precession thereof.

39. In a means for laying guns with reference to relatively rapidly moving targets, a sight including a pair of rate of turn type gyroscopes mounted on a gun so as to be turned as the target is followed, pivotal supports for each gyroscope permitting precession about axes at right angles to the axes of turn of the gun, one being responsive to turning of the gun and sight in azimuth and the other to tilting in elevation, centralizing means and damping means acting about the precession axis of both gyroscopes,

means for varying the former with the time of flight of the shell, means for maintaining the 40. An angular rate generating device for fire control, comprising a gyroscopic rotor and rotor bearing frame, a trunnionaxis for said frame adapted to mount the same for precession on a target following device and including a plurality of leaf springs for pivotally supporting and yieldingly centralizing said frame, a damping means for damping precessional movements of said frame about said axis, and means for adjusting the stiffness of at least a portion of a said springs, said springs and damping means being so constructed and arranged that the chartially equal to the time of flight of the shell.

41. An angular rate generatingdevice for fire control, comprising a gyroscopic rotor and rotor bearing frame mounted for precession about an axis, spring means yieldably centralizing said gyroscope about said axis, a damping means for damping precessional movements of said frame about said axis, means for keeping the damping coeificient of said damping means constant during temperature fluctuations, and means for adjusting the stiffness of said springs with changes in the time of flight of the shell.

42. An angular rate generating device for flre control, comprising a gyroscopic rotor and rotor bearing frame mounted for precession upon angular movement of the line of sight about an axis, means forresiliently centralizing the position of said gyroscope about its precession axis, viscous damping means for damping the precession movements about said axis, thermostatic means for keeping the damping coefficient of said clamping means constant during temperature fluctuations, and means for adjusting the elastic characteristics of said resilient centralizing means with the time of flight of the shell.

1 CHARLES S. DRAPER.

EDWARD P. BENTLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 7 Re. 22,330 Draper June 8, 1943 1,057,648 Lindhard Apr. 1, 1913 1,407,491 Sperry Feb. 21, 1922 1,531,132 Radford Mar. 24, 1925 1,760,163 Morris May 27, 1930 1,936,442 Willard Nov. 21, 1933 1,955,488 Crane et a1. Apr. 17, 1934 2,232,537 Kollsman Feb. 18, 1941 2,405,068 Tear et a1. July 30, 1946 2,407,191 Tear et a1. Sept. 3, 1946 2,432,613 Fedde Dec. 16, 1947 2,464,195 Burley et al. Mar. 8, 1949 FOREIGN PATENTS Number Country Date 162,304 Great Britain May 5, 1921 749,767 France May 15, 1933 

